Building a CMS from a ground up

My client wants to make a Content management system (CMS). Here is the project brief attached with this message. My client would like to see if you guys can build something like this for my client so my client can re- brand on their name and not have any other companies involved. My client also wants to have a modular system where they can add modules like newsletters that build newsletters in the future I would like to work only with those developers that have extensive experience in building content management system from ground up. You will be requested to show CMS online to evaluate your expertise. You will be evaluated on the quality of work deliverables and workmanship. Please do not quote if above criteria is not fulfilled!